This invention relates to a support for a photographic material, more specifically to a support for a photographic material having excellent recovering property from roll set curl after development processing while maintaining strength.
In recent years, a light-sensitive photographic material has been used for various purposes. For example, it has been known that a light-sensitive material comprising a thin support for a photographic material is effective for miniaturization of a photographing device. However, when a support for a photographic material is made thin, the so-called rigidity is lowered, whereby there is a drawback that conveyability and handling property in a photographing device and in subsequent development processing steps are lowered. In order to solve such a drawback, mechanical strength, particularly elastic modulus of a support for a photographic material is required to be made higher than that of a conventionally used support for a photographic material.
As a conventionally used plastic film support, there may be mentioned representatively triacetyl cellulose (TAC) and polyethylene terephthalate (PET).
A TAC film which has been mainly used as a roll film has characteristics that it has no optical anisotropy and has high transparency, and further excellent characteristic that roll set curl can be straightened after development processing. However, the TAC film has a drawback that mechanical strength is inherently poor, whereby it cannot be made thin.
On the other hand, a PET film has excellent productivity, mechanical strength and dimensional stability so that it has been mainly used as a sheet film such as an X-ray film, However, when the PET film is used in a rolled state which has been generally used in a light-sensitive photographic material, there is a drawback that roll set curl after development processing can hardly be straightened, whereby handling property is poor. Thus, its application range is limited.
As a means of improving recovering property from roll set curl of the PET film, there has been proposed a copolymerized PET film to which hydrophilicity is imparted by using an aromatic dicarboxylic acid having a metal sulfonate group as a copolymer component (see Japanese Provisional Patent Publication No. 244446/1989). However, according to this method, a large amount of the copolymer component should be contained in order to obtain sufficient recovering property from roll set curl, whereby excellent characteristics inherently possessed by PET such as mechanical strength and dimensional stability are lost to lose superiority to TAC.
Further, in Japanese Provisional Patent Publication No. 93937/1992, there has been proposed a light-sensitive photographic material having excellent recovering property from roll set curl and mechanical characteristics such as tear strength and folding endurance due to lamination of polyesters having different water contents. Also, according to this method, a large amount of an aromatic dicarboxylic acid having a metal sulfonate group as a copolymer component should be contained in order to obtain sufficient recovering property from roll set curl, whereby characteristics of a copolymerized polyester layer such as mechanical strength and dimensional stability are lost. Thus, the above method is effective for improving characteristics such as tear strength and folding endurance which are considered to be greatly influenced by property of a polyester layer with a low water content constituting an inner layer, but it is not effective for improving characteristics such as mechanical strength, particularly elastic modulus which is property of a whole film.